A high sensitivity, high speed, silicon-based X-ray detector requiring a minimum of auxiliary electronics for amplification is proposed. The detector would consist of two silicon PIN junctions on either side of a high atomic number metal. High resistivity silicon for the intrinsic regions of the PIN junctions will be grown by chemical vapor deposition (CVD). The PIN junctions would be operated under reverse bias to deplete the intrinsic region, maximize sensitivity, and increase response speed. Quantum efficiency of the proposed detector will be markedly enhanced at high X-ray energies by incorporating a thin, high atomic number layer into the detector structure. Orienting the detector at a sharp angle to the X-ray beam would increase effective path-length and therefore the interaction probability. Thickness of the high atomic number layer would be chosen to maximize photoelectron escape probability. Performance characteristics should be ideal for fabricating tomographic arrays.